Our research group focused on compounds having a naphthyridine skeleton and continued intensive research thereon to develop compounds having excellent pharmacological effects. As a result, we found novel compounds having anti-inflammatory activity, anti allergic activity, immune regulating activity, analgesic activity and the like (Japanese Unexamined Patent Publication No. 304775/1995).
The novel compounds have potent anti-inflammatory effects but their alagesic effects are not completely satisfactory.
An object of the invention is to provide novel naphthyridine derivatives having potent analgesic effects.
We synthesized compounds in which the substituents at 1-position of the naphthyridine ring varied and carried out pharmacological screening of the same. Consequently we found a group of novel compounds having highly potent analgesic activity as compared with conventional compounds, and accomplished the present invention.